We moved the three older kids into the same room while we've/I've been working on the latest project.
That means that every night there is lots of laughing from them that leads to me yelling down the stairs "get back on your bed, NOW!".
When it's time to clean I hear "that's not my mess, I shouldn't have to clean it up".
In the mornings someone usually screams "don't look at me!" and "get back on your side of the room!"
There are now 3 twin beds, 3 dressers, 3 toy bins and mucho grande messes.
Please notice how my children make their beds in a perfect military fashion. Also notice the humidifier box that my son uses to keep his cars corralled (who needs a toy box).
One unexpected advantage that possibly outweighs the late night slumber parties is that there is only one room to clean. I might "forget" to move my boy back to his room when the project is over.